1. Field of the Invention
The present invention concerns a cosmetic composition containing specific long chain unsaturated retinol fatty acid esters useful for skin care treatment for chronoaging conditions and dermatologic disorders to provide skin radiance without substantial irritation.
2. The Related Art
Skin is subject to deterioration through dermatologic disorders and normal aging (chronoaging) as well as extrinsic factors (environmental). Dermatologic disorders, other than chronoaging include acne, follicular and lesional papules, actinic keratoses, oily skin and rosacea.
Chronoaging results in the thinning and general degradation of skin. As skin naturally ages, there is reduction in the cells and blood vessels that supply the skin. There is also a flattening of the dermal-epidermal junction which results in weaker mechanical resistance. Aging individuals increasingly develop facial fine lines, wrinkles, leatheriness, yellowing or sallowness, sagging, mottling (hyperpigmentation), age spots and the general signs of aging.
Extrinsic factors are primarily those caused by exposure to sun. Changes are most prominent in light skinned individuals who burn easily and tan poorly. The results of photo damage may be identical to those of aging except may appear at an accelerated rate. Wrinkling, yellowing, leatheriness, mottling and hyperpigmentation are all associated with sun damage. Most disturbing to many individuals is the wrinkling effect. As a result, there have been many articles reporting cosmetic treatments aimed at the elimination of wrinkles.
Skin care compositions containing retinoids have become quite prominent in recent years. Retinoic acid, also known as Vitamin A acid or Tretinoin, is well known for treatment of acne. Even more recently, the retinoids have been suggested as treatment against photoaging and sun damage. For instance, U.S. Pat. No. 4,603,146 discloses Vitamin A acid in an emollient vehicle to prevent skin aging. U.S. Pat. No. 4,877,805 suggests a number of retinoids as useful for restoring and reversing sun damage in human skin. EP 0 631 772 describes use of retinol in combination with an irritation ameliorating amount of glycolic acid.
Recent clinical investigations of the responses of normal skin to retinol as compared to retinoic acid indicate that retinoic acid rather than retinol irritates skin and is the erythemogenic agent. Kang et al, "Application of Retinol to Human Skin In Vivo ("Induces Epidermal Hyperplasia and Cellular Retinoid Binding Proteins Characteristic of Retinoic Acid but Without Measurable Retinoic Acid Levels or Irritation" Journal of Investigative Dermatology #4, (Oct. 95), pp. 549-555. It appears that a cellular retinol binding protein (CRBP) in the epidermis converts retinol to its retinol esters by inhibiting the synthesis of retinol to retinoic acid. Supra. The regulation of retinoic acid concentrations to control skin irritation is lost when a consumer just applies retinol to the skin.
Retinols, as well as, retinol (vitamin A) and many of its esters, are known in the art to require formulation with stabilizing systems to provide products which do not lose activity in storage. See Chem. Abs., 120: 330825s describing U.S. Ser. No. 926,606 filed Aug. 6, 1992 now abandoned by Johnson & Johnson Consumer Products, Inc.; Chem Abs. 120: 330820m describing JP 06 32774 owned by Shiseido Co. Ltd.
Short chain retinol derivatives, such as retinyl acetate and retinyl propionate, are known to lose activity in storage. Retinyl palmitate having a C.sub.16 chain is also known as the most stable of the available vitamin A esters. (See ldson, B. "Vitamins and the Skin", Cosmetics & Toiletries, Vol. 108, December 1993, p. 79, 86.
It has now been discovered that skin fatty acid esters of retinol which are both unsaturated and long chain (C.sub.18 -C.sub.30) may be formulated without requiring a stabilizing system to retain their activity during storage. This discovery is particularly surprising because it appears to go against conventional teachings, that saturated, and not saturated bonds are more stable since compounds containing saturated bonds would be expected to retain their activity longer than compounds containing unsaturated bonds.
These esters have also been observed to enhance overall skin radiance and treat dermatological and chronoaging conditions without skin irritation.
Another object of the present invention is to provide a skin composition which treats dermatological disorders (such as acne, follicular and lesional papules, actinic keratoses, oily skin and rosacea) and chronoaging conditions (including wrinkling and fine lines, leatheriness, yellowing, sagging, sallowness, mottling (hyperpigmentation), age spots and general aging signs) at least or more effectively than retinol and its esters which are saturated.
These and other objects of the present invention will become more readily apparent from the following summary and detailed discussion.